In many technical processes it is necessary to meter fluids at high speeds with great accuracy. A typical example of this is the metering of fuel to an automobile gasoline-engine, where each cylinder is supposed to be supplied with an exact amount of fuel each time the air intake valve of that cylinder opens. The amount of fuel supplied to each cylinder depends on the status of the engine, i.e., it depends on the power the engine is delivering, its temperature, ambient air pressure etc. To ensure maximum engine efficiency and minimum air pollution by the exhaust gases, the air-fuel mass ratio entering each cylinder of the engine should be close to 14.5 at which ratio all fuel is burnt and all oxygen in the air is used. To meet these maximum conditions the amount of fuel in each fuel pulse delivered to each of the cylinders of the engine should be metered with an accuracy of plus or minus 1% or better. If a central metering element is supplying all cylinders of the engine at the same time, it is necessary that this accuracy be met for each of the cylinders and not only for all the cylinders together. If some of the cylinders get too much fuel and some too little, the engine will run inefficiently and produce unnecessary pollution. Thus, the equal distribution of the fuel between the cylinders is of great importance.
The correct amount of fuel to be metered to each cylinder in the form of pulses, one pulse for each cylinder firing, depends on engine power, air temperature, air pressure, throttle position, engine temperature and several other parameters. This amount can be determined by a microprocessor, the input of which is supplied by the above parameters. Normally the microprocessor outputs one electric pulse for each cylinder firing, the length of which is proportional to the amount of fuel to be metered. Hence the fuel metering element itself should be controllable by electrical signals. In a central metering device for a four cylinder engine the length of this pulse varies between 0.5 to 10 milliseconds and its repetition frequency varies between 5 to 200 pulses per second. These operation conditions are very demanding on mechanical endurance, reliability and long-term metering accuracy of the device.
A typical example of such a metering element is described in Bosch Technische Berichte 3, 1 (November 1969). Essentially it is a fast electromagnetic valve. It consists of a small nozzle to which the fuel is applied at about 100 kPa (1 atmosphere). On the fuel side the nozzle is closed by a cylindrical element made of iron, the face of which is pressed against the entrance to the nozzle by a spring. In this position no fuel can exit from the nozzle.
At the position of the cylindrical element the fuel line is surrounded by a solenoid. If a current is passed through this solenoid, the iron cylindrical element will be slightly retracted from its seat on the nozzle entrance so that fuel can pass through the nozzle. Thus by applying the pulse from the microprocessor, fuel will pass through the nozzle to the engine, the amount of which is proportional to the pulse length. Since the microprocessor issues one pulse for each engine firing, fuel can be metered to the engine in precise amounts.
If a four cylinder engine is supplied by one such metering device, the device will have to be operated up to 200 times a second. This puts a very heavy strain on some of the components of the device, e.g. the cylindrical element and the valve seat. As a result, these parts change slightly in shape with time which affects the metering accuracy of the device. This is especially true for short pulses (0.5-2 milliseconds) where it is difficult to attain the required accuracy even in new devices. Further, using one central metering device for all four cylinders of the engine it is difficult to distribute exactly the same amount of fuel through the manifold to each of the cylinders. If this is not attained with good precision, the engine runs inefficiently and causes air pollution. The same is true for engines where each cylinder is supplied through a separate fuel metering device if these devices differ in their metering accuracy due to wear or for other reasons. Finally, it should be mentioned that this type of fuel metering device is expensive to produce because of the close mechanical tolerances that have to be met to ensure the proper functioning of the device. For these reasons a new fuel metering device has been developed which circumvents the disadvantages mentioned above. This invention uses a continuous jet of fuel exiting from a nozzle under high pressure which is directed into a fuel return tube. By controlling the divergence of the jet, the amount of fuel missing the fuel return tube can be controlled.
It is therefore a primary object of this invention to provide an novel method of controlling the divergence of a continuous stream of liquid from the normal axis of the stream.
It is a further object of the present invention to provide an improved method for controlling the divergence of the continuous stream by controlling the amplitude of a periodic oscillating nozzle delivering the stream.
It is a further object of the present invention to provide a method of the character described to control the amplitude of the nozzle by use of an electric signal.
It is an additional object of the present invention to provide a method of the character described where the electric signal is one of alternating current or voltage.
It is a further object of the present invention to provide a method of the character described where at least a part of the continuous stream of liquid enters a receptor during each periodic oscillation of the nozzle.
It is another object of the present invention to employ this method to control the delivery of a continuous stream of liquid to a receptor by passing the continuous stream through an interceptor.